Biomodification of Bond Performance of Coconut Fiber in Cement Mortar to Enhance Damping Behavior

In this study, bio-modified coconut fiber as a renewable and eco-friendly material was used to enhance the damping properties of cement mortar and reduce the adverse effects of vibration. The chemical bonds, relative crystallinity and microscopic morphology test results of original and bio-modified coconut fibers were compared and analyzed to explore the effect of biomodification with laccase on the physicochemical properties of coconut fibers. The compressive strengths, porosities, densities, and damping properties of cement mortars were tested and used to evaluate the effect of biomodified fiber on the properties of samples. The loss of compressive strength caused by incorporating fiber was effectively reduced with biomodification treatment. More specifically, the compressive strengths of cement mortar containing 0.5 vol.% original fiber were decreased by 36.84% compared with plain cement mortar (41.04 MPa), while the cement mortar with 0.5 vol.% biomodified fiber exhibited a much higher compressive strength of 35.8 MPa. The strength improvement effect can be attributed to the lower air-entrainment effect of biomodified fiber. Moreover, the damping enhancement effect of fiber was also effectively enhanced with biomodification treatment. The loss tangent of the cement mortar containing 0.5 vol.% biomodified fiber was 17.97% higher than that of cement mortar with 0.5 vol.% original fiber and 26.82% higher than that of plain cement mortar, respectively. An interfacial slip model was further established to explain the damping enhancement mechanism.